Fin Field Effect Transistor (FinFET) Device Structure with Interconnect Structure

ABSTRACT

A semiconductor device structure and method for forming the same are provided. The semiconductor device structure includes a first metal layer formed over a substrate and a dielectric layer formed over the first metal layer. The semiconductor device structure further includes an adhesion layer formed in the dielectric layer and over the first metal layer and a second metal layer formed in the dielectric layer. The second metal layer is electrically connected to the first metal layer, and a portion of the adhesion layer is formed between the second metal layer and the dielectric layer. The adhesion layer includes a first portion lining with a top portion of the second metal layer, and the first portion has an extending portion along a vertical direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/062,822, filed on Oct. 5, 2020, and entitled “Fin Field EffectTransistor (FinFET) Device Structure with Interconnect Structure,” whichis a continuation of U.S. application Ser. No. 16/050,013, filed on Jul.31, 2018, and entitled “Fin Field Effect Transistor (FinFET) DeviceStructure with Interconnect Structure,” now U.S. Pat. No. 10,796,955,which is a divisional of U.S. application Ser. No. 14/813,775, filed onJul. 30, 2015, and entitled “Fin Field Effect Transistor (FinFET) DeviceStructure with Interconnect Structure,” now U.S. Pat. No. 10,332,790,which claims the benefit of U.S. Provisional Application No. 62/175,849filed on Jun. 15, 2015, and entitled “Fin Field Effect Transistor(FinFET) Device Structure with Interconnect Structure,” the entirety ofwhich is incorporated by reference herein. This application is relatedto the following co-pending and commonly assigned patent application:U.S. application Ser. No. 14/799,258, filed on Jul. 14, 2015, andentitled “Fin Field Effect Transistor (FinFET) Device Structure withInterconnect Structure”, now U.S. Pat. No. 9,536,826, the entirety ofeach is incorporated by reference herein.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are typically fabricated bysequentially depositing insulating or dielectric layers, conductivelayers, and semiconductive layers of material over a semiconductorsubstrate, and patterning the various material layers using lithographyto form circuit components and elements thereon. Many integratedcircuits are typically manufactured on a single semiconductor wafer, andindividual dies on the wafer are singulated by sawing between theintegrated circuits along a scribe line. The individual dies aretypically packaged separately, in multi-chip modules, for example, or inother types of packaging.

In the fabrication of semiconductor devices, the size of semiconductordevices has been continuously reduced in order to increase devicedensity. Accordingly, a multi-layered interconnect structure isprovided. The interconnect structure may include one or more conductivelines and via layers.

Although existing interconnect structures and methods of fabricatinginterconnect structures have been generally adequate for their intendedpurposes, they have not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a three-dimensional view of an interconnect structure on afin field effect transistor (FinFET) device structure, in accordancewith some embodiments of the disclosure.

FIGS. 2A-2P show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure,in accordance with some embodiments of the disclosure.

FIG. 2P′ shows an enlarged representation of region A of FIG. 2P, inaccordance with some embodiments of the disclosure.

FIGS. 3A-3E show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure,in accordance with some embodiments of the disclosure.

FIG. 3C′ shows an enlarged representation of region B of FIG. 3C, inaccordance with some embodiments of the disclosure.

FIG. 3E′ shows an enlarged representation of region C of FIG. 3E, inaccordance with some embodiments of the disclosure.

FIGS. 4A-4E show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure,in accordance with some embodiments of the disclosure.

FIG. 4C′ shows an enlarged representation of region D of FIG. 4C, inaccordance with some embodiments of the disclosure.

FIG. 5 shows a trench-via structure with an over-recessed trenchopening.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Some variations of the embodiments are described. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements. It should be understood that additionaloperations can be provided before, during, and after the method, andsome of the operations described can be replaced or eliminated for otherembodiments of the method.

Embodiments for forming a semiconductor structure with an interconnectstructure are provided. The interconnect structure includes a number ofmetallization layers formed in a dielectric layer (such as inter-metaldielectric, IMD). One process for forming interconnect structures is thedual damascene process.

FIG. 1 shows a three-dimensional view of an interconnect structure on afin field effect transistor (FinFET) device structure 100, in accordancewith some embodiments of the disclosure.

The FinFET device structure 100 includes a substrate 102. The substrate102 may be made of silicon or other semiconductor materials.Alternatively or additionally, the substrate 102 may include otherelementary semiconductor materials such as germanium. In someembodiments, the substrate 102 is made of a compound semiconductor suchas silicon carbide, gallium arsenic, indium arsenide, or indiumphosphide. In some embodiments, the substrate 102 is made of an alloysemiconductor such as silicon germanium, silicon germanium carbide,gallium arsenic phosphide, or gallium indium phosphide. In someembodiments, the substrate 102 includes an epitaxial layer. For example,the substrate 102 has an epitaxial layer overlying a bulk semiconductor.

The FinFET device structure 100 also includes one or more fin structures20 (e.g., Si fins) that extend from the substrate 102. The fin structure20 may optionally include germanium (Ge). The fin structure 20 may beformed by using suitable processes such as photolithography and etchingprocesses. In some embodiments, the fin structure 20 is etched from thesubstrate 102 using dry etch or plasma processes.

An isolation structure 22, such as a shallow trench isolation (STI)structure, is formed to surround the fin structure 20. In someembodiments, a lower portion of the fin structure 20 is surrounded bythe isolation structure 22, and an upper portion of the fin structure 20protrudes from the isolation structure 22, as shown in FIG. 1 . In otherwords, a portion of the fin structure 20 is embedded in the isolationstructure 22. The isolation structure 22 prevents electricalinterference or crosstalk.

The FinFET device structure 110 further includes a gate stack structureincluding a gate dielectric layer 32 and a gate electrode 34. The gatestack structure is formed over a central portion of the fin structure20. In some other embodiments, the gate stack structure is a dummy gatestack and is replaced later by a metal gate (MG) after high thermalbudget processes are performed.

As shown in FIG. 1 , spacers 36 are formed on the opposite sidewalls ofthe gate electrode 34. The source/drain (S/D) structures 24 are formedadjacent to the gate stack structure. The contact structures 40 areformed over the source/drain (S/D) structures 24, and a first metallayer 104 is formed over the contact structure 40. A trench-viastructure 50 is formed over the first metal layer 104. A second metallayer (not shown) will be formed on the trench-via structure 50. Thetrench-via structure 50 is disposed between the first metal layer 104and the second metal layer and is configured to electrically connect tothe first metal layer 104 and the second metal layer.

FIG. 1 is a simplified view of the interconnect structure including afirst metal layer and trench-via structure 50 over the fin field effecttransistor (FinFET) device structure 100. Some features, such as theinter-layer dielectric (ILD) layer and doped regions, are not shown inFIG. 1 .

FIGS. 2A-2P show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure50 a, in accordance with some embodiments of the disclosure. FIGS. 2A-2Pshow a trench-first process for forming a dual damascene structure.

As shown in FIG. 2A, the semiconductor device structure 100 includes asubstrate 102. The substrate 102 includes a first region 11 and a secondregion 12. IN some embodiments, the first region 11 is a dense region,and the second region 12 is an isolation region. The substrate 102 maybe made of silicon or other semiconductor materials. Some deviceelements (not shown) are formed in the substrate 102. Device elementsinclude transistors (e.g., metal oxide semiconductor field effecttransistors (MOSFET), complementary metal oxide semiconductor (CMOS)transistors, bipolar junction transistors (BJT), high-voltagetransistors, high-frequency transistors, p-channel and/or n channelfield effect transistors (PFETs/NFETs), etc.), diodes, and/or otherapplicable elements. Various processes are performed to form deviceelements, such as deposition, etching, implantation, photolithography,annealing, and/or other applicable processes. In some embodiments,device elements are formed in the substrate 102 in a front-end-of-line(FEOL) process.

The substrate 102 may include various doped regions such as p-type wellsor n-type wells). Doped regions may be doped with p-type dopants, suchas boron or BF₂, and/or n-type dopants, such as phosphorus (P) orarsenic (As). The doped regions may be formed directly on the substrate102, in a P-well structure, in an N-well structure, or in a dual-wellstructure.

The substrate 102 may further include isolation features (not shown),such as shallow trench isolation (STI) features or local oxidation ofsilicon (LOCOS) features. Isolation features may define and isolatevarious device elements.

As shown in FIG. 2A, a first dielectric layer 106 (such as inter-metaldielectric, IMD) is formed on the substrate 102, and a first metal layer104 a and a second metal layer 104 b are embedded in first dielectriclayer 106. The first metal layer 104 a is in the first region 11 and thesecond metal layer 104 b is in the second region 12. The firstdielectric layer 106 and first metal layer 104 a, second metal layer 104b are formed in a back-end-of-line (BEOL) process.

The first dielectric layer 106 may be a single layer or multiple layers.The first dielectric layer 106 is made of silicon oxide (SiOx), siliconnitride (SixNy), silicon oxynitride (SiON), dielectric material(s) withlow dielectric constant (low-k), or combinations thereof. In someembodiments, the first dielectric layer 106 is made of an extreme low-k(ELK) dielectric material with a dielectric constant (k) less than about2.5. In some embodiments, ELK dielectric materials include carbon dopedsilicon oxide, amorphous fluorinated carbon, parylene,bis-benzocyclobutenes (BCB), polytetrafluoroethylene (PTFE) (Teflon), orsilicon oxycarbide polymers (SiOC). In some embodiments, ELK dielectricmaterials include a porous version of an existing dielectric material,such as hydrogen silsesquioxane (HSQ), porous methyl silsesquioxane(MSQ), porous polyarylether (PAE), porous SiLK, or porous silicon oxide(SiO₂). In some embodiments, the dielectric layer 106 is deposited by aplasma enhanced chemical vapor deposition (PECVD) process or by a spincoating process.

In some embodiments, the first metal layer 104 a and the second metallayer 104 b are independently made of copper (Cu), copper alloy,aluminum (Al), aluminum alloy, tungsten (W), tungsten alloy, titanium(Ti), titanium alloy, tantalum (Ta) or tantalum alloy. In someembodiments, the first metal layer 104 is formed by a plating method.

An etch stop layer 110 is formed over the first dielectric layer 106.The etch stop layer 110 may be a single layer or multiple layers. Theetch stop layer 110 protects the underlying layers, such as the firstdielectric layer 106 and also provides improved adhesion for layersformed subsequently.

The etch stop layer 110 is made of a metal-containing material, such asan aluminum-containing material. In some embodiments, thealuminum-containing material is aluminum nitride, aluminum oxide oraluminum oxynitride. The aluminum-containing material may increase thespeed of the semiconductor device 100.

A second dielectric layer 112 is formed over the etch stop layer 110.The second dielectric layer 112 may be a single layer or multiplelayers. The second dielectric layer 112 is made of silicon oxide (SiOx),silicon nitride (SixNy), silicon oxynitride (SiON), dielectricmaterial(s) with low dielectric constant (low-k), or combinationsthereof. In some embodiments, the second dielectric layer 112 is made ofan extreme low-k (ELK) dielectric material with a dielectric constant(k) less than about 2.5.

An antireflection layer 114 and a hard mask layer 116 are sequentiallyformed over the second dielectric layer 112. In some embodiments, theantireflection layer 114 is made of nitrogen-free material, such assilicon oxycarbide (SiOC). In some embodiments, the hard mask layer 116is made of a metal material, such as titanium nitride (TiN), tantalumnitride (TaN), or tungsten nitride (WN). The hard mask layer 116 made ofmetal material is configured to provide a high etch selectivity relativeto the second dielectric layer 112 during the plasma process.

A tri-layer photoresist structure 120 is formed on the hard mask layer116. The tri-layer photoresist structure 120 includes a bottom layer124, a middle layer 126 and a top layer 128. In some embodiments, thebottom layer 124 is a bottom anti-reflective coating (BARC) layer whichis used to reduce reflection during the photolithography process. Insome embodiments, the bottom layer 124 is made of nitrogen-freematerial, such as silicon rich oxide, or silicon oxycarbide (SiOC). Insome embodiments, the middle layer 126 is made of silicon-basedmaterial, such as silicon nitride, silicon oxynitride or silicon oxide.

The top layer 128 may be a positive photoresist layer or a negativephotoresist layer. In some embodiments, the top layer 128 is made ofPoly (methyl methacrylate) (PMMA), Poly (methyl glutarimide) (PMGI),Phenol formaldehyde resin (DNQ/Novolac) or SU-8. In some embodiments,the ratio of the thickness of the bottom layer 124 to the thickness ofthe middle layer 126 is in a range from about 4 to about 8.

Afterwards, the top layer 128 is patterned to form a patterned top layer128 as shown in FIG. 2B, in accordance with some embodiments of thedisclosure. The patterned top layer 128 includes a first portion 128 a,a second portion 128 b and a third portion 128 c.

After the top layer 128 is patterned, the middle layer 126 is patternedby using the patterned top layer 128 as a mask as shown in FIG. 2C, inaccordance with some embodiments of the disclosure. As a result, thepattern of the top layer 128 is transferred to the middle layer 126 toform the patterned middle layer 126.

After the middle layer 126 is patterned, the bottom layer 124 ispatterned by using the patterned middle layer 126 as a mask as shown inFIG. 2D, in accordance with some embodiments of the disclosure.

Afterwards, the hard mask layer 116 is patterned by using the patternedbottom layer 124 as a mask as shown in FIG. 2E, in accordance with someembodiments of the disclosure. Afterwards, the tri-layer photoresiststructure 120 is removed by an etching process. Therefore, the patternedhard mask layer 116 is obtained, and it includes a first portion 116 a,a second portion 116 b and a third portion 116 c. The first width W₁ isformed between the first portion 116 a and the second portion 116 b. Thesecond width W₂ is formed between the second portion 116 b and the thirdportion 116 c. In some embodiments, the first width W₁ is substantiallyequal to the second width W₂.

After the hard mask layer 116 is patterned, a second photoresiststructure 220 is formed over the patterned hard mask layer 116 as shownin FIG. 2F, in accordance with some embodiments of the disclosure. Thesecond photoresist structure 220 includes a bottom layer 224, a middlelayer 226 and a top layer 228.

The top layer 228 of the second photoresist structure 220 is firstlypatterned to form a patterned top layer 228 as shown in FIG. 2G, inaccordance with some embodiments of the disclosure. The patterned toplayer 228 includes a first portion 228 a, a second portion 228 b and athird portion 228 c. A third width W₃ is formed between the firstportion 228 a and the second portion 228 b. A fourth width W₄ is formedbetween the second portion 228 b and the third portion 228 c. The thirdwidth W₃ is substantially equal to the fourth width W₄. The third widthW₃ between the first portion 228 a and the second portion 228 b issmaller than the first width W₁ (as shown in FIG. 2E) between the firstportion 116 a and the second portion 116 b of the patterned hard masklayer 116.

Afterwards, the middle layer 226 is pattered by using the patterned toplayer 228 as a mask as shown in FIG. 2H, in accordance with someembodiments of the disclosure.

After the middle layer 226 is pattered, the bottom layer 224 and aportion of antireflection layer 114 is removed as shown in FIG. 2I, inaccordance with some embodiments of the disclosure. The portion ofantireflection layer 114 is removed by a first etching process 310 toform a first recess 302 a in the first region 11 and a second recess 302b in the second region 12. The sidewalls of the recess 302 are verticalto the antireflection layer 114. The width of the first recess 302 a issubstantially equal to the width of the second recess 302 b.

The first plasma process 310 includes using a first etch gas includingoxygen gas (O₂), carbon dioxide (CO₂) or another applicable gas. Inaddition to gas, the first etching process 310 may be fine-tuned withvarious parameters, such as pressure, power, temperature and/or othersuitable parameters.

After forming the first recess 302 a and the second recess 302 b, theantireflection layer 114 is etched through and a portion of the seconddielectric layer 112 is removed by a second etching process 330 as shownin FIG. 2J, in accordance with some embodiments of the disclosure.

As a result, the recess 302 is elongated to form a first opening 304 aand a second opening 304 b. It should be noted that the sidewalls of thefirst opening 304 a and second opening 304 b are vertical to the seconddielectric layer 112. In other words, the first opening 304 a and thesecond opening 304 b both have a substantially vertical profile.

The second etching process 330 is performed by using a second etch gasincluding fluorine-containing gas, nitrogen (N₂), oxygen (O₂) orcombinations thereof. The fluorine-containing gas includes nitrogenhexafluoroethane (C₂F₆), tetrafluoromethane (CF₄), trifluoromethane(CHF₃), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈),octofluorocyclobutane (C₄F₈), or combinations thereof.

Afterwards, the second photoresist structure 220 is removed as shown inFIG. 2K, in accordance with some embodiments of the disclosure.Therefore, the patterned hard mask layer 116 is exposed.

After the second photoresist structure 220 is removed, the seconddielectric layer 112 and the etch stop layer 110 are etched through toexpose the first metal layer 104 by a third etching process 350 as shownin FIG. 2L, in accordance with some embodiments of the disclosure.

Therefore, a first via opening 306 a and a first trench opening 308 aare formed and they collectively constitute a first trench-via structurefor use as a dual damascene cavity. The first via opening 306 a has afirst width D₁. In some embodiments, the first width D₁ is in a rangefrom about 30 nm to about 60 nm. The first trench opening 308 a has athird width D₃. In some embodiments, the third width D₃ is greater thanthe first width D₁.

If the first width D₁ is smaller than 30 nm, the dimensions are toosmall to fill the conductive material. If the first width D₁ is greaterthan 60 nm, the pitch between two adjacent via openings may be smallerthan the predetermined value.

The third etching process 350 is performed by using a third etch gasincluding fluorine-containing gas, nitrogen (N₂), oxygen (O₂) orcombinations thereof. The fluorine-containing gas includes nitrogenhexafluoroethane (C₂F₆), tetrafluoromethane (CF₄), trifluoromethane(CHF₃), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈),octofluorocyclobutane (C₄F₈), or combinations thereof.

The third etch gas used in the third etching process 350 furtherincludes a diluting gas, such as an inert gas, for example argon (Ar) orhelium (He). The diluting gas is used to decrease the loading effect.

After the third etching process 350, an adhesion layer 130 is formed onsidewalls and the bottom surfaces of the via openings 306 a, 306 b andtrench openings 308 a, 308 b as shown in FIG. 2M, in accordance withsome embodiments of the disclosure. In addition, the adhesion layer 130is also formed on the hard mask layer 116.

The adhesion layer 130 is used to provide improved adhesion for layersformed subsequently. In some embodiments, the adhesion layer 130 is madeof titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalumnitride (TaN), or aluminum nitride (AlN).

After formation of the adhesion layer 130, a portion of the etch stoplayer 110 is removed to expose the first metal layer 104 a and thesecond metal layer 104 b by a fourth etching process 370, as shown inFIG. 2N, in accordance with some embodiments of the disclosure.

In some embodiments, the fourth etching process 370 is a dry etchingprocess, such as plasma process. During the fourth etching process 370,the electric field concentrates at corners region of the opening.Therefore, corner region may be damaged. As shown in FIG. 2N, a portionof the adhesion layer 130 is also removed, especially at corner regions.As a result, the adhesion layer 130 becomes a discontinuous layer.

The adhesion layer 130 includes a first portion 130 a and a secondportion 130 b below the first portion 130 a. The first portion 130 a isadjacent to or lines with the trench openings 308 a, 308 b, and thesecond portion 130 b is adjacent to or lines with the via openings 306a, 306 b.

In some embodiments, the first portion 130 a of the adhesion layer 130has an extended bottom surface in a horizontal direction (in parallel tothe top surface of the metal layer 104). The extended bottom surface islarger than a top surface of the first portion 130 a of the adhesionlayer 130.

In some embodiments, the second portion 130 b of the adhesion layer 130has a sloped surface. In some embodiments, the second portion 130 b ofthe adhesion layer 130 has a top surface which is not parallel to a topsurface of the first metal layer 104 a, 104 b.

After the fourth etching process 370, a conductive feature 142 is formedin the trench openings 308 a, 308 b, the via opening 306 a, 306 b and onthe hard mask layer 116, as shown in FIG. 2O, in accordance with someembodiments of the disclosure.

The conductive feature 142 is electrically connected to the first metallayer 104. In some embodiments, the conductive feature 142 is referredto a second metal layer. The first metal layer 104 embedded in the firstdielectric layer 106 and the conductive feature 142 embedded in seconddielectric layer 112 construct a portion of the interconnect structure50 a. In some embodiments, the conductive feature 142 is made of copper(Cu), copper alloy, aluminum (Al), aluminum alloys, or combinationsthereof.

It should be noted that the adhesion between the dielectric layer 112(especially low-k material) and the conductive feature 142 is poor. Ifno adhesion layer 130 formed between the dielectric layer 112 and theconductive feature 142, the conductive feature 142 may be shrunk by abaking process which is performed after FIG. 2P. Therefore, the adhesionlayer 130 is configured to increase the adhesion and prevent theshrinkage problem of the conductive feature 142.

Afterwards, the antireflection layer 114, the hard mask layer 116 andsome conductive feature 142 out of the trench openings 308 a, 308 b areremoved, as shown in FIG. 2P, in accordance with some embodiments of thedisclosure. FIG. 2P′ shows an enlarged representation of region A ofFIG. 2P, in accordance with some embodiments of the disclosure. In someembodiments, the antireflection layer 114 and hard mask layer 116 areremoved by a chemical mechanical polishing (CMP) process.

As shown in FIG. 2P, a portion of the conductive feature 142 issurrounded by the adhesion layer 130, but not all of the conductivefeature 142 is surrounded by the adhesion layer 130. The conductivefeature 142 includes an upper portion (or called as trench portion) 142a, a lower portion 142 c (or called as via portion), and a middleportion (or called as interface portion) 142 b between the upper portion142 a and the lower portion 142 c. No obvious interfaces exist betweenthe upper portion 142 a and the middle portion 142 b, and between themiddle portion 142 b (or interface portion) and the lower portion 142 c.The dashed lines shown in FIG. 2P are used to clarify the disclosure.

The upper portion 142 a has a constant width W₅, and the lower portion142 c has a constant width W₆. However, the middle portion 142 b has atapered width which is gradually tapered from the upper portion 142 a tothe lower portion 142 c. In other words, the middle portion 142 b has apair of curved sidewalls. The width W₅ is larger than the width W₆, andthe tapered width is smaller than the width W₅ and larger than the widthW₆.

It should be noted that the adhesion layer 130 is formed between theconductive feature 142 and the second dielectric layer 112, and portionsof upper portion 142 a and the lower portion 142 c of the conductivefeature 142 are not formed on the adhesion layer 130. But, a portion ofthe middle portion 142 b of the conductive feature 142 is not formed onthe adhesion layer 130. Instead of contacting with the adhesion layer130, the middle portion 142 b of the conductive feature 142 is directlycontact with the second dielectric layer 112 because the adhesion layer130 is a discontinuous layer.

As mentioned above, the adhesion layer 130 includes the first portion130 a and the second portion 130 b. As shown in FIG. 2P and 2P′, thefirst portion 130 a lines with the upper portion 142 a of the conductivefeature 142, and the second portion 130 b lines with the lower portion142 c of the conductive feature 142. A portion of the interconnectstructure is surrounded by the etch stop layer. More specifically, aportion of the conductive feature 142 is surrounded by the etch stoplayer 110.

While performing the fourth etching process 370 (as shown in FIG. 2N),the first metal layers 104 a, 104 b are exposed and some by-products(such as metal-containing material) may form on the via openings 306 a,306 b. However, if the undesirable by-products are deposited on thesidewalls of the via openings 306 a, 306 b, the widths of the viaopenings 306 a, 306 b may become smaller, and the conductive feature 142are difficult to fill into the via openings 306 a, 306 b. In addition,some metal-containing material may re-sputter on the sidewalls of thevia openings 306 a, 306 b. As a result, the adhesion between theconductive feature 142 and the second dielectric layer is decreased. Theconductive feature 142 may be easily delaminated while performing abaking process after the removing process shown in FIG. 2P. Therefore,the adhesion layer 130 is formed as shown in FIG. 2M before the metallayers 104 a, 104 b are exposed. The adhesion layer 130 protects thesidewalls of the via openings 306 a, 306 b from being polluted andincrease the adhesion between the conductive feature 142 and the seconddielectric layer 112. In addition, the delamination problem of theconductive feature 142 is also prevented.

FIGS. 3A-3E show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure50 b, in accordance with some embodiments of the disclosure.Interconnect structure 50 b is similar to, or the same as, interconnectstructure 50 a as shown in FIG. 2P, except the shape of the trenchopenings 308 a, 308 b is different. Processes and materials used to forminterconnect structure 50 b may be similar to, or the same as, thoseused to form the interconnect structure 50 a and are not repeatedherein.

As shown in FIG. 3A, the third etching process 350 is performed on thesecond dielectric layer 112, the first trench openings 308 a and thefirst via openings 306 a are formed in the first region 11, and thesecond trench openings 308 b and the second via openings 306 b areformed in the second region 12. The first trench openings 308 a and thefirst via openings 306 a collectively constitute a first trench-viastructure for use as a dual damascene cavity. The second trench openings308 b and the second via openings 306 b collectively constitute a secondtrench-via structure for use as a dual damascene cavity.

As shown in FIG. 3A, the trench openings 308 a, 308 b have extendingportions. The trench opening 308 a includes an upper portion withvertical sidewalls and the extending portion with curved bottomportions. An intersection between the vertical sidewall and the curvedbottom portion is called as tip P₁. In some embodiments, the tip P₁ islocated at a position that is a lower than a highest point Q₁ of the viaopening 306 a.

The trench-via structure has a depth H₁. The trench opening 308 a has awidth D₃. The aspect ratio (H₁/D₃) is a ratio of the depth H₁ to thewidth D₃. The upper portion of the trench opening 308 a has a depth H₂,and the extending portion has a depth H₃. In some embodiments, a ratio(H₃/H₂) of the depth H₃ to the depth H₂ is in a range from about 0.5 toabout 100.

An aspect ratio of an opening is defined as a depth to a width of theopening. It should be noted that the aspect ratio of the firsttrench-via structure has a higher aspect ratio, compared with thetrench-via structure in FIG. 2L. If the high aspect ratio of the firsttrench-via structure is etched, more etching time is needed to obtain adesired profile.

FIG. 5 shows a trench-via structure with over-recessed trench opening506. The trench opening 508 is formed above the via opening 506. Asmentioned above, the corner regions of the trench opening will be easilyattached by the third etching process 350. If the etching time isincreased, the corner region of the trench opening 508 is over-recessed.As a result, the conductive formed in the via opening 506 and the trenchopening 508 subsequently may contact with other regions. Theover-recessed trench opening 508 is not a desired profile. In addition,if a number of the trench-via structures are located at isolated regionsand the dense region, an over-etched trench structure may be produced,due to the loading effect.

Therefore, in order to prevent the trench opening from beingover-etched, when the trench opening is formed, the extending portion ofthe trench opening should be controlled within a range by controllingthe etching parameters of the third etching process 350. For example,when the ratio (H₃/H₂) of the depth H₃ to the depth H₂ is controlledwithin a range of from about 0.5 to about 100, the third etching process350 is stopped. The adhesion layer 130 is used to protect the sidewallsof the trench opening 308 a, 308 b before the trench opening 308 a, 308b are over-etched.

After the third etching process 350, the adhesion layer 130 is formed onsidewalls and the bottom surfaces of the via openings 306 a, 306 b andtrench openings 308 a, 308 b as shown in FIG. 3B, in accordance withsome embodiments of the disclosure. The adhesion layer 130 isconformally formed on the first trench-via structure with the firsttrench opening 308 a and the first via opening 306 a and the secondtrench-via structure with the second trench opening 308 b and the secondvia opening 306 b.

The adhesion layer 130 is used to provide improved adhesion for layersformed subsequently. In addition, since some etching process willperform on the trench-via structure, the adhesion layer 130 formed onthe trench openings 308 a, 308 b and via openings 306 a, 306 b areconfigured to protect the trench-via structure from being over-etched.

After forming the adhesion layer 130, a portion of the etch stop layer110 is removed to expose the first metal layer 104 a and the secondmetal layer 104 b by a fourth etching process 370, as shown in FIG. 3C,in accordance with some embodiments of the disclosure.

As mentioned above, the corner regions are attached by the fourthetching process 370. As a result, the adhesion layer 130 becomes adiscontinuous layer. The adhesion layer 130 includes the first portion130 a and the second portion 130 b below the first portion 130 a. Thefirst portion 130 a is not connected to the second portion 130 b. Thefirst portion 130 a is adjacent to the trench openings 308 a, 308 b, andthe second portion 130 b is adjacent to the via opening 306 a, 306 b.The first portion 130 a has the extending portion along a verticaldirection which is vertical to a top surface of the metal layer 104 a,104 b.

In some embodiments, the first portion 130 a of the adhesion layer 130has an extended bottom surface in a horizontal direction (in parallel tothe top surface of the metal layer 104). The extended bottom surface islarger than a top surface of the first portion 130.

In some embodiments, the second portion 130 b of the adhesion layer 130has a sloped top surface. In some embodiments, the second portion 130 bof the adhesion layer 130 has a top surface which is not parallel to atop surface of the first metal layer 104 a, 104 b.

When a portion of the adhesion layer 130 is removed, the trench opening138 a provide more areas to form the conductive feature 142. As aconsequence, a greater volume of the conductive feature 142 is depositedon the trench-via structure compared with the embodiments withoutremoving the portion of the adhesion layer 130, and the resistance ofthe interconnect structure 50 b is reduced.

FIG. 3C′ shows an enlarged representation of region B of FIG. 3C, inaccordance with some embodiments of the disclosure. The first portion130 a of the adhesion layer 130 has a first surface 131 which is indirect contact with the second dielectric layer 112. The first surface131 is vertical to a top surface of the first metal layers 104 a, 104 b.A lowest point t₁ is located at the first surface 131. In addition, thelowest point t₁ is located at a position that is higher than a highestpoint R₁ of the second portion 130 b of the adhesion layer 130. In otherwords, the extending portion has a tip t₁ located at a position that islower than the highest point R₁ of the second portion 130 b of theadhesion layer 130.

After the fourth etching process 370, the conductive feature 142 isformed in the trench openings 308 a, 308 b, the via openings 306 a, 306b and on the hard mask layer 116, as shown in FIG. 3D, in accordancewith some embodiments of the disclosure.

Afterwards, the antireflection layer 114, the hard mask layer 116 andsome conductive feature 142 out of the trench openings 308 a, 308 b areremoved, as shown in FIG. 3E, in accordance with some embodiments of thedisclosure. In some embodiments, the antireflection layer 114 and hardmask layer 116 are removed by a chemical mechanical polishing (CMP)process.

The conductive feature 142 includes a trench portion 142 a, interfaceportion 142 b and via portion 142 c. The interface portion 142 b isbetween the trench portion 142 a and the via portion 142 c. Theinterface portion 142 b has a pair of curved sidewalls.

FIG. 3E′ shows an enlarged representation of region C of FIG. 3E, inaccordance with some embodiments of the disclosure. A portion of theinterface portion 142 b is in direct contact with the second dielectriclayer 112. A portion of the interface portion of the conductive feature142 has a tapered width that is gradually tapered from the trenchportion 142 a towards to the via portion 142 c.

FIGS. 4A-4E show cross-sectional representations of various stages offorming a semiconductor device structure with an interconnect structure50 c, in accordance with some embodiments of the disclosure.Interconnect structure 50 c is similar to, or the same as, interconnectstructure 50 a as shown in FIG. 2L, except the shape of the trenchopenings 308 a, 308 b is different. Processes and materials used to forminterconnect structure 50 c may be similar to, or the same as, thoseused to form the interconnect structure 50 a and are not repeatedherein.

As shown in FIG. 4A, the third etching process 350 is performed on thesecond dielectric layer 112, the trench openings 308 a and the viaopenings 306 a are formed in the first region 11, and trench openings308 b and the via openings 306 b are formed in the second region 12. Thebottoms of the trench openings 380 a, 308 b have a smooth V-shapedshape.

After the third etching process 350, the adhesion layer 130 is formed onsidewalls and the bottom surfaces of the via openings 306 a, 306 b andtrench openings 308 a, 308 b as shown in FIG. 4B, in accordance withsome embodiments of the disclosure.

The adhesion layer 130 includes a first portion 130 a and a secondportion 130 b below the first portion 130 a. The adhesion layer 130 is adiscontinuous layer, and the first portion 130 a is not connected to thesecond portion 130 b. The first portion 130 a is adjacent to the trenchopenings 308 a, 308 b, and the second portion 130 b is adjacent to thevia opening 306 a, 306 b. Since the bottoms of the first the trenchopenings 380 a, 308 b have a smooth V-shaped shape, the bottom of thefirst portion 130 a of the adhesion layer 130 also has a smooth V-shapedshape.

After forming the adhesion layer 130, a portion of the etch stop layer110 is removed to expose the first metal layer 104 a and the secondmetal layer 104 b by the fourth etching process 370, as shown in FIG.4C, in accordance with some embodiments of the disclosure. FIG. 4C′shows an enlarged representation of region D of FIG. 4C, in accordancewith some embodiments of the disclosure.

As mentioned above, the corner regions are attached by the fourthetching process 370. As a result, the adhesion layer 130 becomes adiscontinuous layer. The adhesion layer 130 includes a first portion 130a and a second portion 130 b below the first portion 130 a. The firstportion 130 a is adjacent to the trench openings 308 a, 308 b, and thesecond portion 130 b is adjacent to the via openings 306 a, 306 b.

The bottom of the first portion 130 a of the adhesion layer 130 has asmooth V-shaped shape. The extending tip t₁ is located at a lowestposition of the a smooth V-shaped shape. A bottom of the first portion130 a of the adhesion layer 130 has a first rounded sidewall 133 aconnected to the extending tip t₁ and a second rounded sidewall 133 bconnected to the extending tip t₁, and the first rounded sidewall 133 aand the second rounded sidewall 133 b are symmetric in relation to theextending tip t₁.

After the fourth etching process 370, the conductive feature 142 isformed in the trench openings 308 a, 308 b, the via openings 306 a, 306b and on the hard mask layer 116, as shown in FIG. 4D, in accordancewith some embodiments of the disclosure.

Afterwards, the antireflection layer 114, the hard mask layer 116 andsome conductive feature 142 out of the trench openings 308 a, 308 b areremoved, as shown in FIG. 4E, in accordance with some embodiments of thedisclosure. In some embodiments, the antireflection layer 114 and hardmask layer 116 are removed by a chemical mechanical polishing (CMP)process.

The first portion 130 a of the adhesion layer 130 has the extending tipt₁, and the extending tip t₁ is located at a position that is lower thana highest point of the via portion 142 b of the conductive feature 142.

Embodiments for forming a semiconductor device structure and method forformation the same are provided. The semiconductor device structureincludes a FinFET structure formed over a substrate, and an interconnectstructure formed over the FinFET structure. The interconnect structureincludes a dual damascene structure with a trench-via structure. Atrench opening and a via opening are formed in a dielectric layer, and aconductive feature is filled into the trench opening and the via openingto form the trench-via structure.

An adhesion layer is formed on the trench-via structure before the firstmetal layer is exposed. The adhesion layer is a discontinuous layer andhas an extending portion. The adhesion layer is configured to improvethe adhesion between the dielectric layer and conductive feature, andprevent the trench from being over-etched. Therefore, the delaminationproblem and the shrinkage problem of the conductive feature areprevented. Furthermore, the performance of the semiconductor devicestructure is improved.

In some embodiments, a semiconductor device structure is provided. Thesemiconductor device structure includes a first metal layer formed overa substrate and a dielectric layer formed over the first metal layer.The semiconductor device structure further includes an adhesion layerformed in the dielectric layer and over the first metal layer and asecond metal layer formed in the dielectric layer. The second metallayer is electrically connected to the first metal layer, a portion ofthe adhesion layer is formed between the second metal layer and thedielectric layer. The adhesion layer includes a first portion liningwith a top portion of the second metal layer, and the first portion hasan extending portion along a vertical direction.

In some embodiments, a semiconductor device structure is provided. Thesemiconductor device structure includes a first metal layer formed overa substrate and a dielectric layer formed over the first metal layer.The semiconductor device structure includes an adhesion layer formed inthe dielectric layer and over the first metal layer and a second metallayer formed in the dielectric layer. The adhesion layer is formedbetween the second metal layer and the dielectric layer, and the secondmetal layer includes a via portion and a trench portion above the viaportion. The adhesion layer includes a first portion adjacent to thetrench portion of the second metal layer, the first portion has anextending tip, and the extending tip is located at a position which islower than a highest point of the via portion of the second metal layer.

In some embodiments, a method for forming a semiconductor devicestructure is provided. The method includes forming a first metal layerover a substrate and forming an etch stop layer over the first metallayer. The method includes forming a dielectric layer over the etch stoplayer and forming a trench opening and a via opening in the dielectriclayer. The trench opening has an extending portion. The method includesforming an adhesion layer on sidewalls and bottom surfaces of the trenchopening and the via opening and removing a portion of the etch stoplayer directly above the first metal layer and removing a portion of theadhesion layer to expose a portion of the dielectric layer. The methodincludes filling a second metal layer in the via opening and the trenchopening, and the second metal layer is electrically connected to thefirst metal layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a semiconductor devicestructure, the method comprising: forming a first conductive feature ina first dielectric layer over a substrate; forming an etch stop layerover the first conductive feature; forming a second dielectric layerover the etch stop layer; forming a trench opening and a via opening inthe second dielectric layer, wherein a bottom surface of the trenchopening slopes downward toward the etch stop layer as the bottom surfaceextends away from the via opening toward a sidewall of the trench;forming an adhesion layer on sidewalls and bottom surfaces of the trenchopening and the via opening; removing a portion of the adhesion layerand a portion of the etch stop layer to expose the first conductivefeature, removing the portion of the adhesion layer exposing an exposedportion of the second dielectric layer along the bottom surface of thetrench immediately adjacent the via opening; and filling the via openingand the trench opening with a second conductive feature, wherein thesecond conductive feature is electrically connected to the firstconductive features.
 2. The method of claim 1, wherein removing theportion of the adhesion layer and the portion of the etch stop layer isperformed at least in part by a plasma etch process.
 3. The method ofclaim 1, wherein after removing, the adhesion layer is discontinuous. 4.The method of claim 1, wherein removing the portion of the adhesionlayer and the portion of the etch stop layer removes a portion of thesecond dielectric layer along a bottom of the trench opening adjacentthe via opening.
 5. The method of claim 1, wherein the first conductivefeature is electrically coupled to a source/drain region.
 6. The methodof claim 1, wherein the bottom surface of the trench opening is curved.7. The method of claim 1, wherein after removing the portion of theadhesion layer, the adhesion layer continuously slopes upward from theexposed portion toward a sidewall of the trench opening.
 8. A method forforming a semiconductor device structure, the method comprising: forminga dielectric layer over a conductive feature; forming a trench openingand a via opening in the dielectric layer, wherein a distance from theconductive feature to a top of a sidewall of the via opening is greaterthan a distance from the conductive feature to a bottom of a sidewall ofthe trench opening to form a recess; forming an adhesion layer onsidewalls and bottom surfaces of the trench opening and the via opening,the adhesion layer completely filling the recess; etching the adhesionlayer to expose the conductive feature, wherein the etching exposes andremoves a portion of the dielectric layer at a top of the via opening;and forming a metal feature over the adhesion layer.
 9. The method ofclaim 8, wherein a lowest point of the recess is adjacent the sidewallof the trench.
 10. The method of claim 8, wherein a lowest point of therecess is midway between the sidewall of the trench opening and asidewall of the via opening.
 11. The method of claim 8, furthercomprising: forming an etch stop layer over the conductive feature,wherein the dielectric layer is formed over the etch stop layer, whereinetching the adhesion layer comprises etching the etch stop layer. 12.The method of claim 8, wherein after etching the adhesion layer, theadhesion layer adjacent sidewalls of the trench opening is disconnectedfrom the adhesion layer adjacent sidewalls of the via opening.
 13. Themethod of claim 8, wherein the etching the adhesion layer is performedusing a plasma process.
 14. The method of claim 13, wherein an electricfield in the plasma process concentrates at corners of the via opening.15. A method for forming a semiconductor device structure, the methodcomprising: forming a first metal feature over a substrate; forming adielectric layer over the first metal feature,; forming a trench and avia in the dielectric layer, wherein a width of the trench is greaterthan a width of the via, wherein a sidewall of the trench extends closerto the first metal feature than a top of a sidewall of the via to form arecess; forming an adhesion layer in the trench and the via, theadhesion layer extending continuously from a sidewall of trench to abottom of the via, wherein the adhesion layer completely fills therecess; removing a portion of the adhesion layer to expose an exposedportion of the dielectric layer along a top of the via; removingportions of the exposed portion of dielectric layer; and forming asecond metal feature in the via and the trench, wherein the second metalfeature is electrically connected to the first metal feature.
 16. Themethod of claim 15, wherein the dielectric layer has a single continuouscomposition.
 17. The method of claim 15, further comprising: forming anetch stop layer over the first metal feature, wherein the dielectriclayer is formed over the etch stop layer; and after forming the adhesionlayer, removing a portion of the etch stop layer to expose the firstmetal feature.
 18. The method of claim 15, wherein the second metalfeature directly contacts the dielectric layer.
 19. The method of claim15, wherein a width of the second metal feature continuously narrows ina transition from the trench to the via.
 20. The method of claim 15,wherein, after forming the second metal feature, an upper surface of thedielectric layer slopes continuously upward from the adhesion layer inthe via to the adhesion layer in the trench.